Method of making steel



Patented Nov. 7, 1939 PATENT OFFlCE 2,119,151 ma'rnon or MAKING STEELJames G. Vignos, Canton, Ohio, assignor to Ohio- Fern-AlloysCorporation, Canton, Ohio, a corporation of Ohio No Drawing. ApplicationFebruary 5, 1937. Serial No.- 124,281

, 4 Claims. (Cl. 75-45) The invention relates to the manufacture of ironand steel, and more especially to the production of iron andsteel andits alloys from a molten bath of iron, comparatively low in carbon 5 andcommercially satisfactorily low in other metallic and non-metallicimpurities, with the exception of iron oxide, by removing the excessiron oxide, recarburizing and, if desirable, alloying a this base metalto give the desired finished analyl sis.

The invention contemplates primarily the production of the relativelypure iron base metal by oxidizing the carbon, manganese, silicon andother impurities, removing them from the metal, in so far as theequilibrium reactions between an oxidizing slag and metal low in carbonwill permit. To obtain an iron or steel that is low in carbon and otherimpurities is extremely difficult and costly under present practice, dueto the type of raw materials required and the time necessary forcompleting the reactions. Under the methods now in use it is almostimpossible to have a metal free from the products of deoxidation, whenthis is accomplished by the use of manganese, silicon,

aluminum or other deoxidizers.

The objects of the invention are to provide a method of making iron andsteel and its alloys of high quality, by shortening the time required anusing cheaper raw materials. These objects may be attained by obtaininga molten metal that is cheaply produced and having a higher carboncontent than desired in the base metal to be produced,'and intermixingthe molten metal with a molten oxidizing slag in such manner that thecarbon content of the metal is reduced and manganese oxide, siliconoxide and other oxides, are removed in the slag, producing a base metallow in carbon, and substantially free from impurities except iron oxide.Said base 40 vmetal may then be transferred to a suitable furnace wherethe iron oxide is reduced and additions are made to produce any desiredanalysis by standard and well known methods.

The method implied in this invention consists in first obtaining amolten metal containing at least .05% carbon, and mixing the metal witha a molten oxidizing slag, in such a way that a reaction is set upbetween the carbon and the slag, causing considerable evolution of gas,and reduction of the carbon content. The manganese oxide, silicon oxide,and other oxides, are taken up in the slag. .This produces a metal lowerin carbon, higher in iron oxide, but almost free from other impurities.

The molten metal produced in this operation may then be transferred toan electric furnace, or other suitable furnace, the iron oxide reduced,and additions made to make any desired analysis 1 by. standard and wellknown methods.

From the above, it is apparent that elimination 5 of carbon is extremelyrapid, and that the oxidizing slag must have sufficient iron oxidecontent, so that it can react with the carbon in the metal.

To further illustrate the invention, but not to 10 limit the scope ofthe invention in any way, molten metal of high carbon content can beblown down in a Bessemer furnace to a suitable carbon content, or ametal of suitable carboncontent can be produced in an open hearth fur-1E nace; for example-approximately .15 to .50 carbon.

To produce a metal of that carbon range'is a comparatively easyoperation under our present methods of refining iron and steel. However,to 20 carry the carbon content lower requires considerable time andfuel, and is hard on the furnace refractories; thus making the removalof the carbon expensive. Further, before it can be properly deoxidizedit is necessary to remove the slag, 25 I which is high in iron oxide, orlower the iron oxide in the slag and metal by using ferro-manganese,ferro-silicon, etc., in which there is considerable loss of these costlydeoxidizers and alloy agents. The products of this deoxidization are 30always a source of contamination and give rise to dirty steels ifconsiderable skill is not employed in their use. The present inventionovercomes these difilculties by removing from the furnace the metal whenit has reached the desired carbon 35 content and separating it from itsslag.

For further lowering. the carbon and removing the impurities from thismetal it is mixed with a slag containing a sufficient amount 'of ironoxide, preferably at least 10%, which has been 40 previously melted andmade fluid by suitable additions in a separate furnace. The mixing ofthe metal and slag can be accomplished in many ways, suchas pouring themetal into the slag, rolling it in a rotary furnace, etc. In thisinve'ntion the mixing is mainly accomplished by the v evolution of thecarbon monoxide produced by the chemical reaction of the carbon on theiron oxide in the slag. After the reaction between the metal and slag iscomplete, which is evident by 50 the quieting of the boiling actiondueto the evolution of gas, the metal then separates from the slag bygravity and the metal is lower in carbon and richer in iron oxide. Thismetal while still molten is then transferred to anelectric furnace 55 orother suitable furnace for removal of the iron oxide by standard andwell known methods and. can be alloyed in any desired manner to give therequired analysis.

From these examples it is apparent that. the present invention departsvery radically from our present methods employed in making iron andsteel and its alloys. The main point of deviation in this invention frompresent practice is that the metal is removed from the refining furnaceand separated from its slag for the final elimination of carbon andimpurities by a new slag prepared in a separate furnace. After removingthe carbon to the desired point, the metal while still molten isfinished in another furnace. This deviation from present practice can bereadily understood when we consider our present methods of making ironand steel and its alloys.

The present open hearth practice is to eliminate the carbon and finishthe heat to the desired point in one furnace, using the same slagthroughout by making suitable additions to it as required. Presentelectric furnace practice varies a great deal in regard to the slags andmethods of handling the slag. The conventional practice in both acid andbasic furnaces is to melt down, slag oil and put on new slag forfinishing the heat. In some cases the same slag is used throughout theheat and additions are made to the slag to bring about the desiredfinished slag and metal to the correct analysis. practice is to blow theheat down to the desired carbon and remove it from the converter.

In each of the above examples of our present practice we find that themetal is finished under a desirable slag without removing it from thefurnace or converter. In no case is the metal removed from the meltingfurnace separated from its slag for the final elimination of carbon bymixing it with a new molten slag obtained from a suitable slag meltingfurnace, and the resulting metal while still molten placed in a refiningfurnace for bringing the analysis to the desired point.

For anyone who is conversant with our present metallurgical practice, itis obvious that the above process is capable of wide application becausethe process is extremely flexible and can be applied to make any of ourpresent analyses of iron and steel and its alloys.

I claim:

1. The process of treating ferrous metals which comprises forming a bathof molten ferrous metal having a higher carbon content than desired inthe base metal to be produced, oxidizing this bath of metal until thecarbon content is lowered to approximately .05% to .50%, then forming aseparate bath of molten oxidizing slag containing sumcient oxide toappreciably reduce the carbon content in the metal and incapable ofeliminat ing an appreciable amount of phosphorus, intermixing the moltenmetal containing the above mentioned amount of carbon with the moltenoxidizing slag whereby a reaction is set up between the slag and thecarbon in the metal causing a reduction of the carbon content in themetal accompanied by a strong evolution of gas, and eliminating from themetal and absorbing by the slag the manganese, silicon and similaroxidizable elements that are oxidized, and separating the metal from theslag, producing a base metal Bessemer lower in carbon, higher in ironoxide, and substantially i'ree from other impurities.

2. The process of treating ferrous metals which comprises forming a bathof molten ferrous metal having a higher carbon content than desired inthe base metal to be produced, oxidizing this bath of metal until thecarbon content is lowered to approximately .05% to .50%, then forming aseparate bath of molten oxidizing slag containing sufiicient oxide toappreciably reduce the carbon content in the metal and incapable ofeliminating an, appreciable amount of phosphorus, intermixing the moltenmetal containing the above mentioned amount of carbon with the moltenoxidizing slag whereby a reaction is set up between the slag and thecarbon in the metal causing a reduction of the carbon content in themetal accompanied by a strong evolution of gas and eliminating from themetal and absorbing by the slag the manganese, silicon and similaroxidizable elements that are oxidized, and separating the metal from theslag, producing a base metal lower in carbon, higher in iron oxide, andsubstantially free from other impurities and then reducing the ironoxide in the metal.

3. The process of treating ferrous metals which comprises forming a bathof molten ferrous metal having a higher carbon content than desired inthe base metal to be produced, oxidizing this bath of metal until thecarbon content is lowered to approximately .05% to 50%, then forming aseparate bath of molten oxidizing slag incapable of eliminating anappreciable amount of phosphorus and containing over 10% iron oxide,intermixing the molten metal containing the above mentioned amount ofcarbon with the molten oxidizing slag whereby a reaction is set upbetween the slag and the carbon in the metal causing reduction of thecarbon content in the metal accompanied by a strong evolution of gas andeliminating from the metal and absorbing by the slag the manganese,silicon andsimilar oxidizable elements that are oxidized, and separatingthe metal from the slag, producing a base metal lower in carbon, higherin iron oxide, and substantially free from other impurities.

4. The process of treating ferrous metals which comprises forming a bathof molten ferrous metal having a higher carbon content than desired inthe base metal to be produced, oxidizing this bath of metal until thecarbon content is lowered to approximately .05% to .50%, then forming aseparate bath of molten oxidizing slag containing suflicient oxide toappreciably reduce the carbon content in the metal and incapable ofeliminating an appreciable amount of phosphorus, intermixing the moltenmetal containing the above mentioned amount of carbon with the moltenoxidizing slag whereby a reaction is set up between the slag and thecarbon in the metal causing a reduction of the carbon content in themetal accompanied by a strong evolution of gas and eliminating from themetal and absorbing by the slag the manganese, silicon and similaroxidizable elements that are oxidized, and separating the metal from theslag, producing a base metal lower in carbon, higher in iron oxide, andsubstantially free from other impurities, then reducing the iron oxidein the metal and alloying the metal to any desired analysis.

' JAMES C. VIGNOS.

